An organic light-emitting element (also referred to as “organic electroluminescence element” or “organic EL element”) is an electronic element including a pair of electrodes and an organic compound layer placed between the pair of electrodes. An electron and a hole are injected from the pair of electrodes, and then the electron and the hole recombine in the organic compound layer to produce an exciton of a luminous organic compound. The organic light-emitting element emits light upon return of the exciton to its ground state.
Recent development of the organic light-emitting elements is significant and the developed elements have, for example, the following features. The light-emitting elements can be driven at low voltages, emit light beams having various wavelengths, have high-speed responsiveness, and can be reduced in thickness and weight.
By the way, the creation of a compound suitable for the organic light-emitting element has been vigorously performed heretofore. This is because the creation of a compound having an excellent element lifetime characteristic is important for providing a high-performance organic light-emitting element.
An organometallic complex to be used as a phosphorescent light-emitting material is included in the compounds created heretofore. The organometallic complex is specifically, for example, an iridium complex described in PTL 1. In addition, another example of the metal complex to be used as a constituent material for the organic light-emitting element is such a metal complex as described in PTL 2. Meanwhile, a metal complex disclosed in PTL 3 or PTL 4 is available as a metal complex to be incorporated as a host into an emission layer together with the iridium complex.